This cache is a nod towards an area a friend and I passed through a few years ago when running the Miner's Trail
It's a bit more than a quick park'n'grab: about a 3 hour loop walk to a height of 822m but the result is an easy-to-find ammo can container.
This is one of my favourite walks in the area. The tracks themselves are good, although be prepared for some long steep sections. I'd recommend doing it anticlockwise. A good map of the area including the main tracks is here Mahu Whenua Walking Tracks, Arrowtown (pdf). Cache is near the intersection of tracks 10 and 11.
Why Phantom's Ridge you ask? A nod towards a friend, and an activity that could have made him a phantom as well.